Devices for performing chemical analysis have in recent years become miniaturized. For example, microfluidic devices have been constructed using microelectronic fabrication and micromachining techniques on planar substrates such as glass or silicon which incorporate a series of interconnected channels or conduits to perform a variety of chemical analysis such as capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). Other applications for microfluidic devices include diagnostics involving biomolecules and other analytical techniques such as micro total analysis systems (.mu. TAS). Such devices, often referred to in the art as "microchips," also may be fabricated from plastic, with the channels being etched, machined or injection molded into individual substrates. Multiple substrates may be suitably arranged and laminated to construct a microchip of desired function and geometry. In all cases, the channels used to carry out the analyses typically are of capillary scale dimension.
To fully exploit the technological advances offered by the use of microfluidic devices and to maintain the degree of sensitivity for analytical techniques when processing small volumes, e.g., microliters or less, connectors which introduce and/or withdraw fluids, i.e., liquids and gases, from the device, as well as interconnect microfluidic devices, are a crucial component in the use and performance of the microfluidic device.
A common technique used in the past involves bonding a length of tubing to a port on the microfluidic device with epoxy or other suitable adhesive. Adhesive bonding is unsuitable for many chemical analysis applications because the solvents used attack the adhesive which can lead to channel clogging, detachment of the tubing, and/or contamination of the sample and/or reagents in or delivered to the device. Furthermore, adhesive bonding results in a permanent attachment of the tubing to the microfluidic device which makes it difficult to change components, i.e., either the microfluidic device or the tubing, if necessary. Thus assembly, repair and maintenance of such devices become labor and time intensive, a particularly undesirable feature when the microfluidic device is used for high throughput screening of samples such as in drug discovery.
To avoid problems associated with adhesive bonding, other techniques have been proposed in the past, e.g., press fitting the tubing into a port on the microfluidic device. However, such a connection typically is unsuitable for high-pressure applications such as HPLC. Additionally, pressing the tubing into a port creates high stress loads on the microfluidic device which could lead to fractures of the channels and/or device.
Other methods involved introducing liquids into an open port on the microfluidic device with the use of an external delivery system such as a pipette. However, this technique also is undesirable due to the possibility of leaks and spills which may lead to contamination. In addition, the fluid is delivered discretely rather than continuously. Moreover, the use of open pipetting techniques does not permit the use of elevated pressure for fluid delivery such as delivered by a pump, thereby farther restricting the applicability of the microfluidic device.
Therefore, a need exists for an improved microfluidic connector which is useful with all types of microfluidic devices and provides an effective, high pressure, low fluid dead volume seal. The connector also should overcome the disadvantages and limitations described above, including chemical compatibility problems resulting from the use of adhesive bonding techniques.